I'm going to guess most of you have heard of Sudoku. It's become enormously popular over the past two dozen years it has gone from an unknown numbers game to probably the second-most popular puzzle game, right behind crossword puzzles. It's one of those easy-to-learn/hard-to-master type games that keeps people coming back to it.

Despite the name, it's not actually a Japanese game. An early version of the game first appeared in French newspapers around 1895. The modern version of the game was introduced by Howard Garns, a retired architect in Indiana, in 1979 using the name Number Place. It's unclear if Garns was familiar with the similar French puzzle. About a half decade later, it was introduced into Japan by Maki Kaji using simplified rules and making the puzzle symmetrical. Then 13 years later, it spread to Hong Kong, and that is when it started to explode world wide. There are all kinds of variants at this point, but the base game remains the most popular form.

There are a number of mathematical properties that have emerge about the game. Mathematicians have proven that the fewest possible clues are 17. In some variants there are fewer, but we are talking about the base game with the default rules. That's the number of all possible puzzles using only 17 clues, mind you, if we add more clues the number of possible puzzles goes up high enough that it's safe to say we have plenty of puzzles to go around.

Anyway, what prompted me to write this post was a Numberphile video I happened to see. Numberphile makes math videos if you are unfamiliar with them, usually talking to university mathematicians about curious proofs and things like that. Pretty nerdy stuff. This Numberphile video was different in that it features Simon Anthony, a dude who makes his living from Sudoku (crazy, isn't it?), who introduces us to a really unique property of Sudoku called the Phistomephel Ring. This is really cool! Watch and learn.

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David LaSpina is an American photographer and translator lost in Japan, trying to capture the beauty of this country one photo at a time and searching for the perfect haiku. He blogs here and at laspina.org. Write him on Twitter or Mastodon.